Headlight lens



R. N. FALGE HEADLIGHT LENS Aug. 5, 1958 2 Sheets-Sheet 1 Filed April 9, 1954 sNvENToR sm e ATTO R N EY R. N. FALGE HEADL Aug. 5, 1958 Filed April 9, 1954 ATTORNEY United KStates, Patent@ l i l j j 2,846,568 ,j

- HEADLIGHT LENS Robert N. Falge, Anderson, Ind., assignor to `General Motors Corporation, Detroit, Mich., a corporation of v Delaware I Application April 9, 1954, Serial No. 422,213 Y 1 Claim. (c1. 24th-41.4),-

' .This invention relates to vehicle lamps and more particularly, to an improved lens for a vehicle lamp which is adapted to project a trapezoidal beam pattern. yThere has recently been recognition by the vehicle lighting industry of the great advantages to -be gained, in some instances, by th-e use of vehicle head lamps adapted to project a beam of light which defines a trapezoid on a vertical screen and which projects a rectangular `beam pattern on the ground. This is distinguished fromolder-type lamps having a beam pattern which on a vertical screen is generally rectangular and on the ground is fan shaped. By means of the so-called trapezoidal beam, a ground pattern which is rectangular even out to its furthest extent in front of the vehicle and which provides better lateral or side lighting is obtained. Such a pattern greatly improves the distribution of light from the head lamps and has been found to be particularly useful on tractors and similar farm vehicles.

It has been proposed to produce a trapezoidal light pattern by constructing a lens `with a plurality of contiguous surfaces of compound curvature each of which is shaped to :produce a trapezoidal pattern. Thus, the light pattern produced by the entire lens consists of the trapezoidal patterns of each of the contiguous surfaces all superimposed over each other. Because the light distribution within the trapezoidal pattern is determined by the particular shape of the individual surface of compound curvature, it is somewhat difficult to place the light within the trapezoid exactly where it is most needed. In other words, the disadvantage of such a lens structure is that it allows for little exibility in designing a specific trapezoidal lens for a specific job wherein particular light distribution characteristics within the trapezoid are desired. For example, it is often advantageous to provide a hot spot in the uppermost portion of the beam pattern. lt is dicult to accomplish this with the aforementioned type trapezoidal lens because in order to do so would require changing the curvatureof at least some, or perhaps all, of the contigui ous surfaces on the lens.

It is an object of the present invention to provide an improved method for illuminating a generally rectangularly-"shaped horizontal areat- I 2 Another object of the invention'is to produce a lens suitable for use in automotive vehicle head lamps lwhich projects a tarpezoidal beam pattern having improved lighting. characteristics. v i

l Another object of the invention .is the'provision of a lens .for producing a Vtrapezoidal beam pattern which allows for exibility of design to obtain the particular light distribution'characteristics desired.

These and other objects are carried out in accordance with the invention by projecting two beams of light, each of which defines a generally rectangular shape when projected on a vertical screen, the corresponding sides of the rectangular Vbeams being at an angle to each other and the lines of direction :of the beams being at an angle to each other s'that they combined to overlap and forma gen- "ice erally trapezoidal shaped pattern on a vertical screen. This is accomplished by the provision of a head lamp constructed with a lens having two generally rectangular surfaces of compound curvature, with corresponding sides at an angle with respect to each other and having their optical axes also at an angle to each other. Thus, the two generally rectangular surfaces produce beam patterns which are at an angle to each other and which are partially superimposed thereby combining to define a generally trapezoidal pattern on a vertical screen. The lens may additionally beV provided with other pairs ofi similar sur` faces and also with portions to produce a hot spot, the sumtotal of all these surfaces combining to form a generally trapezoidal shape (on a vertical screen) with the light distribution characteristics desired. f

Other objects and advantages of the invention will appear more clearly from the following description of a preferred embodiment and from the drawings in which:

Figure .1 is a front view of the preferred embodiment of the lens;

Figure 2 is a cross-sectional view taken on the line 2 of Fig. l; j v

Fig. 3 is a view taken on a line 3 3 of Figure l;

Figure 3a is a View taken on a line 3 3a of Figure 3; Figure 4is a'view takenV ona line 4 4 of Figure l; 'i

Figure 4a is a view taken on a line 4a 4a of Figure't;

Figure 5 is a view taken on a line 5 5 of Figure l;

Figure 5a is a view taken on a line 5a 5a of Figure 5;

Figure 6 is a view taken on a line 6 6 of Figure l;

Figure 6a is a View taken on a line 6a 6a of Figure 6;

Figure 7 is a view taken on a line 7 7 of Figure l;

Figure 7a is a view taken on a line 7a 7a of Figure 7;

Figure 8 is a view taken on a line 8 8 of Figure l;

Figure 8a is a View taken on a line 8a-8a of Figure 8;

Figure 9 is a view on a vertical screen of a part of the beam pattern projected by the preferred lamp of this nvention; and

Figure l0 is a side View in partial section of a preferred embodiment of the lamp.

Referring now to the drawings, and in particular, to Figure l, there is shown a lens having a plurality of portions A, B, C, D, E, and F, each of these portions having its own particular light spreading, directing and orienting properties, as hereinafter described. Portions C, D, E, and F aresubdivided by the vertical center line of the lens into portions C1, C2, D1, D2, E1, E2, F1, F2, respectively.

Each portion, as for example, portion A, consists of 'a multiplicity of contiguous generally vrectangular surfacesV posed utes.

curvatures of the vertical and horizontal 'superimposed' flutes from which the surfaces are formed.

The direction in which' the beam from any one lens portion is projected is determined by the prism angle of the contiguous surfaces Within that portion with respect'to' the plane of the lens. By the term horizontal prism angle, as used herein, is meant the angle between the tangent to the horizontal curvature of the contiguous surface referred to, and the tangent to the lens curvature at the midpoint on the contiguous surface. l By the term vertil prism angle is meant the angle between the tangent to the vertical curvature of the contiguous surface referred to, and the tangent to the lens curvature at the midpoint on the contiguous surface. Thus, referring to Fig. 3 the horizontal prism angle of the contiguous surfaces in lens por- 3` tion C is and, referring to Fig. 5a, the verticalprisrn angle of the contiguous surfaces in lens portion A is 26. The angular orientation of the beam from `any one lens portion, with respect tothe lens vertical centerline, will be `determined bythe amount of rotation, withinthe plane ofl the. lens, of the contiguous surfaces in that portion with respect to the vertical center line. -In other words, ifa contiguous surface within alens portion has 4a composite curvature which adapts it to a project a rectangular pattern, this rectangular pattern may he rotated clockwise or counter-clockwise by molding the contiguous surface at. anangle inthe planel of the lens-with respect to the vertical center line. ifBy Vthe .term Vangular rotation, as used herein, is meant the'arlgleV between one of the generally vertically extending edges of the contiguous surfaces being referred to, and Vthe Vvertical center line. This can be seen by reference Ito Fig. l, wherein the angular rotation of the contiguous surfaces in lens portion F2 is shown tobe 12.

. The light spread, angular orientation and the vertical and horizontal prism `angles. of the contiguous surfaces in each of the vportions of the ,preferred lens, as shown in Fig. l, .are set forth in the following table.

Fmrimntal Vertical Angular Vertical Horizontal Spread, Spread, Rotation Prism Prism Angle degrees degrees Angle A 12 2 0 26 up.-- 0.

01.---- 20 50 8 countel- 10 Out-right.

' clockwise.

Cz-.-" 20 50 8 clockwise.-. 0 10 Out-left.

Dh..- 20 30 8 counter- 0 6 Out-right.

clockwise.

DL.-. 20 3U 8 clockwise.-- 0 6 Out-left.

E1 28 26 12 counter- 3 Out-right.

' clockwise.

En.--" 28 26 12 clockwise.- 3 Out-left.

F1 28 18 12 eounter- 7 Out-right.

clockwise.

13.-... 28 18 12 clockwise.. 0 7 Out-left.

The function of the optics listed on the above table can best be seen -by reference to Fig. 9 which shows a part of the beam pattern on a vertical screen) projected by the lens ofFig. l when it is mounted in a lamp having a parabolic reflector with a light bulb at the focal point. Portion C1, -of the lens projects the rectangular pattern C1', having `a 20 horizontalspread and a 50 vertical spread. Because of the 8 counterclockwise rotation, the rectangular pattern is at an 8 angle to the vertical centerline as shown. The 10 prism angle, out and to the right (as viewed from behind the lens looking in the direction of the beam) results in `the pattern C1', being displaced out `and to the right of the vertical centerline of the screen. Lens portion C2 projects the rectangular pattern C2. This pattern `C2 has the same light spread as C1' and is therefore identical in size and shapeghowever, the. 8 rotation is clockwiserather than counterclockwise and the 10 prism angle is out and to the left rather than out and to the right. Thus, pattern C2' forms a 16 angle Vwith, and overlaps pattern C1thereby delining a generally trapezoidal shape.

We prefer to,set the rectangular beam patterns at an yangle to each other of from 10 to 80, the combined pattern in 'all instances defining a generally trapezoidal shape. In the embodiment shown, the optical axes of portion C1 and kC2 are at a 20 (10 +10) angle to each other; however, the optical axes may be set at any` angle up -to,50 with respect to each other to accomplish the proper amount yof-overlap. The exact angles used will, of course, depend on the shape of the trapezoid desired.

lBeam patterns C1 and `C1 combine to form the broad outline or periphery of the overall beam pattern of the.

entire lens. The remaining light patterns from other portions of the lens complement the pattern C1-C2 and furnishlight where it is most needed within the pattern. Lens portions D1, E2, and F1 produce patterns D1',

4l E1', F1' respectively. To simplify the Fig. 9, the patterns produced by lens portion D2, E2, and F2 have not been shown; however, it will be obvious from the optics listed in the above table that the patterns projected by these lens portions will bear the same relationship to D1', E1', and F1', respectively, as does C1 to C2. For example, the pattern from F2 is identical in shape to F1 but is rotated clockwise so 'as to be at 24 (2 12) angle to F15 and is displaced out and to the left from the vertical centerline rather than out and to the. right as in the case Of F1.

Lens portions A and B are designed to providepa hot spot within the pattern.- `Portion B produces the rectangular pattern 'B' which, because of the vertical prism angle of 18 up, is directed slightly above the horizontal centerline of the screen so as to fall in the upper portion of the overall beam pattern defined by C1 and C2'. Portion A produces the small but Vintense rectangular pattern A' which is directed 26 up from the horizontal and which therefore fallswithin the upper-portion of B'. It will beV noted that portions A Vand B are-'not rotated and thus, the vertical edgesof the patterns A and B are parallel:Y with the vertical centerline of the screen as shown.

Thus, in the preferred embodiment of the lens, a plus` rality of portions, i. e., A, B, D, E, `and F, are provided' so as to produce patterns which will complement that of C1 and C2 and add light at selected points Within the trapezoid. However, it is to be understood that only por-` tions the same or similar .to C1 and C2 need be used to attain the generally trapezoidal pattern and that other Alens portions, if they are used, can take different forms' depending upon the particular lighting characteristics def sired. As can be seen from- Figs. 3. and 3a to Figs. 8 and 8aY inclusive, a combination of convex and concave fluting is used in each portion of the lens in order to attain the contiguous surfaces of compound curvature. This come bination of concave and convex liuting is preferable for ease of manufacture; however, it is to be understood thatl other combinations might be used. For example, the ilutes may all be convex or they 'may all be concave if desired.

In Fig. 10 there is shown a tractor lamp embodying the invention.` This lamp comprises an outer casing 20 which supports lens 22, identical to that shown in Fig. 1, having positioned behindV it parabolic reflector 24, carrying at its focal point the lighting element 26. The reflector 24 `and lighting element 26 combine to project parallel light rays to lens 22, the lens serving to bend and spread these rays in accordance with the. description recited above.

Someor all of the optics herein shown and described `as incorporated in thelens element may, if desired, be incorporatedinto the reflector by means Well known in the art. For example, a split type reflector withtwo or more portions tilted through an angle with respect to `each yother may, if desired, be used in place of prism angles yon the lens.

This lamp is mounted on a vehicle so that itdirects theV light slightly downwardly and thus, vthe beamv pattern on the ground will be of a generally rectangular shape.

VWhile the lamp shown consists of separate reflector and lens elements, the invention may of course, be embodied in an all-glass type sealed beam unit wherein the reflector and lens form an hermetically sealed bulb for a lighting filament mounted at focus.

From the above description of a preferred embodiment,l it will be clear -that the present invention encompasses lighting devices designed to project at least two light patterns the longitudinal axes of which are at an angle to each other and which overlap so as to'deine, ona vertical screen, a generally trapezoidal shape. Various changesv and modifications of the invention described herein may be made by those skilled in the art without departing from the spirit and principles of the invention. Y

asaeee What is claimed is:

A lens for vehicle headlamps and the like comprising a transparent body divided horizontally into a plurality of portions, each of said portions extending across said lens and having a plurality of contiguous rectangular surfaces of the same compound curvature, some of said lens portions being vertically divided into two sections, the edges of the rectangular surfaces in one of said sections being at an acute angle to the corresponding edges of the rectangular surfaces in the other of said sections and the optical axes of the surfaces in one of said sections being at an angle with respect to the optical aXes of the surfaces in the other of said sections so that said sections are adapted to project, on a screen disposed at a right angle to the optical axis of said lens, rectangular light patterns which are at an acute angle to each other and which overlap to define a generally trapezoidal shape, and each of the remainder of said lens portions having rectangular surfaces of compound curvature with corresponding edges all parallel to each other and being adapted to project a horizontally disposed rectangular light pattern superimposed on a portion of the trapezoidal light pattern.

eerences @Cited in the le of this patent UNITED STATES PATENTS 1,235,675 Ford Aug. 7, 1917 2,122,465 Graves July 5, 1938 2,137,079 Falge Nov. 15, 1938 2,568,494 Geissbuhler Sept. 18 1951 

